<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    #d1{
      border: 10px inset red;
      width: 300px;
      height: 100px;
      /*设置圆角值越大 越圆,超过宽高一半为正圆*/
      border-radius: 100px;
    }
    #d2{
      width: 100px;
      height: 100px;
      border: 1px solid blue;
      padding-left: 50px;
      padding-top: 50px;
      /*默认情况下给元素添加内边距会影响元素宽高*/
      box-sizing: border-box;/*不再影响宽高*/
    }
    body{
      margin: 0;/*去掉自带的8个像素外边距,内容贴边*/
    }
    p,h1,ul{margin: 0;padding: 0}
    input{border: none;padding: 0}
  </style>
</head>
<body>
<input type="text">
<p>这是段落标签p</p>
<h1>这是h1</h1>
<ul>
  <li>aaa</li>
  <li>bbb</li>
  <li>ccc</li>
</ul>
<div id="d1">边框</div>
<div id="d2">内边距</div>
</body>
</html>